Flight control apparatus



June 26, 1951 Filed Aug. 19, 1946 D. L. MARKUSEN FLIGHT CONTROL APPARATUS Sheets-Sheet 1 June 26, 1951 D. L.. MARKusEN V2,553,096

FLIGHT CONTROL APPARATUS 2 Sheets-Sheet 2 Filed Aug. 19, 1946 www latented `une i951 2,558,096 FLGHT CONTROL APPARATUS David L. Markusen, Minneapolis, Minn., assigner to Minneapolis-Honeywell Regulator Company, Minneapolis, Minn., a corporation of Delaware Application August 19, 1946, Serial No. 6%,632

21 Claims.

This invention pertains to the control of an aircraft in flight.

The object of this invention is to provide apparatus for operating the control surfaces of an aircraft in flight and more particularly of an aircraft popularly known as the Flying Wing which is actually a tailless airplane.

The Flying Wing airplane differs radically from the conventional type of airplane. The conventional airplane consists oI" a somewhat elongated fuselage or body portion having wings supported therefrom near the front of the fuselage. The after portion of the fuselage supports the tail surfaces of the airplane. Control of the airplane about its roll axis is obtained by means of ailerons mounted near the extremities of the wings. Con trol of the plane about the turn axis is obtained by means of a rudder mounted in the tail surface. Control of the airplane about the pitch axis is obtained by means of elevators mounted in the tail surface.

In the Flying Wing airplane, the tail is omitted from the structure of the aircraft. The control surfaces are all mounted in the wing. Control of the Flying Wing about its turn axis is obtained by means of two rudders, one of them being mounted in the trailing edge of each wing near the tip thereof. The rudders of the Flying Wing are given this term merely because they, like the conventional rudder, control the movement of the Flying Wing about the turn axis. Structurally they do not resemble the conventional rudder. A rudder of the Flying Wing when operated merely increases the resistance of its particular wing to thereby cause the plane to turn in an arc about the turn axis.

Control of the Flying Wing about its pitch and roll axis is obtained by a single set of two control surfaces. One of these control surfaces is mounted in the trailing edge of each wing inboard of the rudder. These surfaces are so operated that at times they move in the same direction together at which time they function as elevators. At other times they are differentially moved in opposite directions so that they function as the conventional ailerons. These control surfaces are called elevons.

With this brief description of the Flying Wing, an object of this invention is to provide an automatic flight control system or a manually ,operated flight control system for a Flying Wing.

' A further object of this invention is to provide an automatic flight control system for a Flying Wing in which automatic means are provided to stabilize the direction of movement of the air- 2 craft about its turn axis, to provide means for stabilizing the aircraft with respect to its roll axis and to provide means to stabilize the plane with respect to its pitch axis.

A further object of this invention is to provide a control from the directional stabilizing means to the rudder operating means and to the elevon operating means.

A further object of this invention is to provide a control between the means for stabilizing the plane about the roll axis and the elevon operating means and also the rudder operating means.

A further object of this invention is to control the operating means for the elevons of a Flying Wing so that they may be moved concomitantly in the same direction.

A further object of this invention is to control the operating means for the control surface of a Flying Wing by means of several networks in which unbalance of the networks causes the operation of the operating means.

A further object of the invention is to control the operating means for the elevons by means of two interrelated networks, one network functioning to control the operating means so that the elevons move in the same direction so as to function as elevators, and the second network controlling the operating means for the elevons so that they move in opposite directions so as to function as ailerons.

A further object of this invention is to provide two nterrlated networks for controlling the operation of the elevons and in which a voltage signal derived from one network is applied to the other network to control the operation of the elevons in the same direction as elevators and in which a second signal derived from the other network controls the operation of the elevons in opposite directions as ailerons.

A further object of this invention is to provide novel control means for the operation of the elevons of the Flying Wing through two interrelated networks in which a signal derived from one network is applied through a transformer coupling to the second network to cause the operation oi the elevons in the same direction as elevators and in which follow up means driven by said operating means set up a balance signal in said other network to terminate operation of said elevons.

A further object of this invention is to provide novel operating means for the rudders of the Flying Wing so that only one rudder is in operated position at one time.

A further object of this invention is to con- 3 trol the operation of the rudders of a Flying Wing through a series of networks in which a signal derived from a network may cause the operation of one or the other of the rudder operating means, but not both.

A further object of this invention is to provide separate operating means for the two rudders of a Flying Wing which operating means are so interrelated with a control means that one rudder must be in closed position before the other rudder may be moved toward open position.

Other objects and advantages of the invention may be ascertained by referring to the specifica-v tion and drawings and from a consideration of the appended claims; in the drawing,

Figure 1 is a plan view of a Flying Wing or tailless airplane;

Figure 2 is a section along line 2-2 of Figure 1, the dotted lines representing the control members for the aircraft in closed position;

Figure 3 is a functional diagram o f the autopilot system showing the relation between the control elements and the control surfaces of the aircraft; and

Figure 4 is a schematic arrangement of a controlf means for the autopilot.

Y In Figure 1 there is shown a plan view of what may be termed a Flying Wing or tailless airplane.l This airplane as shown has no tail surface as is present in the conventional aircraft. The body of the Flying Wing is made up entirely of the wing itself to decrease the drag effect on the aircraft. The Flying Wing is of the pusher type of aircraft having motors l2 which drive propellers I3 for propelling the craft. Control of the Flying Wing about the pitch and roll axes is obtained by means of elevons I4 which at times move together in the same direction and, therefore. partake of the nature of elevators and at Vother times move in opposite directions when they are in the nature ofV ailer-ons. The elevons may be independently mounted directly upon shafts, not shown, for operative movement. Rudders |5. are used to control the movements of the craft about the turn axis. The rudders, as shown in, Figure 1, are placed near the tip of the wing. Figure 2 represents a section of the right wing showing the details of a rudder and a portion of its operating mechanism. A rudder for each wing comprises two members i5 which are pivoted to the wing. As shown, these members move in a vertical plane toward or away fromv the surface of the wing. The rudder members may be operated through links I6 pivoted thereto. These links have their opposite ends connected or pivoted to a slidable rack bar The rack bar may be driven from a gear I8 which is mounted on a shaft 2|) of a rudder actuating servomotor. A similar arrangement for. Operating the rudder in the left wing of' the airplane from a servomotor operated shaft isI also pro.- vided. The shaft is driven from a servomotor- 30. shown inV Figure 4. A similar shaft for operating the rudder mounted in the left wing` is shown at 2|. This shaft `2| is operated from a servomotor 3|. The servomotors 30 and 3| may be of any conventional form. For example, they may be of the type disclosed in application `Serial No. 447,989, filed June 22, 1942.

These servomotors contain` two relays for controlling the direction of operationk of the out. put shafts.` Such' corresponding relays of the servomotor are indicated: by referenceZ char? acters 32r and 33. In servomotor 3|. the. corre- 4 sponding relays are designated by reference char acters 34 and 35.

The energization of relay coils 32, 33, 34 and 35 is controlled by a pair of relays 43 and 45 forming part of an amplier 40. The relay 43 includes a single pole single throw switch 44 which is biased to open position and is moved to closed position upon energization of the relay 43. Similarly, the relay 45 comprises a single pole single throw switch 46 which is likewise biased to open position and is moved to closed position upon energization of relay 45. One terminal of switch 44 of relay 43 is connected to the positive terminal of a battery, the other tei'- minal of which is grounded. The opposite terminal of switch 44 is connected to relay coil 33 of servomotor 30 and relay coil 35 of servomotor 3|, so that switch 44 controls the energization of relay coils 33 and 35. The switch 46 of relay 45 is likewise connected to a positive terminal of a battery, the other terminal of which is grounded. The other terminal of switch 46 is connected to relay coils 32 and 34 so that switch 46 controls the energization of relay coils' 32r and 34.

The amplifier 40 is of any suitable type inl which one or the other of two relays is energized depending upon the phase of the input voltage. A typical amplier of this type is that shown in the copending application of Albert P. Upton, Serial No.'447,989, led June 22, 1942. As show-nt in the drawing, the ampliiier 40 has input terminals 4| and 42 to which a controly signal maybe applied. The amplifier 46 has its output terminals 41, 48 connected to a source ofV line voltage |00. This source of line voltage may be an inverter of the conventional electrical systemA inV an aircraft or similar source of supply voltage. The switches 44 and 46 of amplier 40 are selec,- tively actuated by their respective relays 43 and 45 which are in the output side of amplifier 40; depending upon the phase relationship of the. input voltage across terminals 4| and 42 with re-l spect to the voltage across terminals 4,1 and 4 8Y supplied. by the line.

rlhe circuit through coil 35 of servomotor 3|y is completed from the opposite end of the coilthrough a lead 39 to an outer contact 66 of a.

limit switch 6|, thence to the inner Contact 63j of the limit switch 6i, lead 53, left Contact.. 64,

of a single pole double throw snap action switch to the middle pole 65. of said snap action switch, thence to ground. The circuit through relay coil 34 of servomotor 3| is completed from. opposite end through lead 'l5 toa left contact 1|. of a single pole double throw snap action switchto the movable arm l2 of said switch and thence toground. The circuit through relay coilv 3,3 of servomotor 39 is completed from its other end through a lead 851, right contact 8| of; a single pole double throw snap action switch to, the middle arm 65 of the switch and thence to groundf The circuit through relay coil 32 is completed from its opposite end through a lead 54 to aright contact of a limit switch to the left contactY 86. of the limit. switcl'nlead ill, right. contact 88, of a snap action switch, arm 'l2 of said switch, and thence to ground.

Limit switch 6| has a left contact 66 which has. a depending portion 62. The arm l2 of thefsnap action switch has a depending portion '13. The arinl 65 of the right snap action switch has a depending portion 61. The limit switchshown at the right has a contact 85 having a. depending portion 89. The depending portions 62 vand 1.3.

assaoee are in the path of movement of a follow-up member 9|. The depending portions 61 and 89 are in the path of movement of a follow-up member 9D. The portions 89, 62 are engaged by members Si), 9i only when the respective ruddrs have reached maximum open position. The member 90 is driven through a mechanical connection 92 from the output shaft 2! of servomotor 30. The follow-up member 9! is driven through a mechanical connection 93 from the output shaft 2| of servomotor 3|.

The member 9o may assume two extreme positions. In one it actuates the depending portion 61 to engage contacts 64 and 65 against the biasing action of the blade supporting contact S5, which biasing action tends to cause engagement of contacts 65 and 8|. In the other eX- treme position, the member 9G will engage depending portion 89 and separate contacts 65 and 86 in opposition to the biasing action of the switch arm which supports Contact 85. The member 94 may assume two extreme positions. In one such position, the right end of member 9| engages the depending portions 'I3 of arm 'l2 and moves its contact into engagement with contact 88 in opposition to the biasing action of arm 'l2 which normally forces its contact against contact 1I. In the other extreme position the movable member 9| has its left edge engaging the depending portion S2 to separate contacts 63 and 68 against the biasing action of the arm supporting contact 6E which normally forces contact 53 against contact 88. As illustrated in Figure e, the movable member Si has been moved from its extreme right position toward the left. At this time the left rudder is in a partly operated position. Ordinarily members Si) and 9i engage portions Bl and 13 to close contacts 64, 65 and 12, 88.

The-operation of the amplifier servomotor arrangement may be brieiiy covered with reference to Figure 4. In Figure 4 the left rudder is .in partly operated position which is attained by operation of a centering means described subsequently. Such partial operation has been made to clearly illustrate the function of the interrelated contacts. Normally contacts 12, 33 and 64, 65 are closed. Assume that a signal is applied to input terminals 4I and 42 of such phase with respect to the voltage across terminals 41 and 48 as to cause energization of relay 43 "n amplifier 4D which results in the closing of switch 44. The closing of switch 44 in effect means that it is desired to turn the plane in the left direction.

A turning action may be effected by decreasing the resistance on one wing or increasing it on the other. This invention accomplishes turning by keeping the resistance of the wing in flight at a minimum. To further this purpose the wing on the outside of a turn has its resistance reduced to a minimum before a turn is initiated. Its rudder is therefore in closed position.

The closing of switch 44 aforesaid completes a. circuit through relay 33 only as far as contact 8l as shown in Figure 4, at which point the circuit is open between contacts 8l and 65. The right servomotor relay is therefore not energized. However, closure of switch 44 does complete a circuit through relay coil 35 through lead 6B, contacts 65, 68, lead 63, contact 64, and arm G7 to ground. The left rudder servomotor therefore operates its rudder and its follow-up means 9i. We may assume that relay 43 of amplifier 4i) when operated calls for more left rudder or more left wing drag or its equivalent and that relay coil 45 in amplifier 4t when energized calls for morev right wing drag or turn to the right. It can now be 'seen that servomotor 3| drives its rudder I5 through output shaft 2l. In ordinary operation the amount of movement given to the follow-up member is dependentupon the magnitude of the amplifier control signal ywhich is derived from networks to be described. A left control signal is canceled by the follow-'up adjustment of wiper 25. It is only in unusual instances that wiper E25 is moved to its extreme left position or until such time as follow-up connection Q3 moves the follow-up member Si to separate contacts E6 and 33. When contacts 63 and 58 are separated, relay coil 35 is deenergiaed. While the member Eli is being operated from its servomotor, membei` 9G remains in its leftward position during which time the right rudder is in unoperated position. Assume now that it is desired to stop the turning of the airplane to the left after member 3l has separated contacts 66 and 68. To stop the left turning action, relay 45 is energize-d to switch 43. Relay coil 32 which is connected to one pole of switch l5 has its circuit open between contacts '52 and 83. However, coil 34 which is also connected to a polo of switch 43 has its circuit completed through lead l0, contact l, and pole I2 to ground. Motor 35 remains inoperative, but motor 3l is operative to drive its output shaft 2|. Coil 34 causes the operation or" shaft 2i in an opposite direction from that obtained by coil 35. Servomctor 3l therefore drives the rudder 5 toward closing position and at the same time drives its followup member 3i toward the right. When the member 9i reaches its rightward position, it separates contacts 'Ei and Il? thereby deenergizing coil 34 and closes contacts i2 and BS. If coil 45 remains energized, upon such closing of contact 12 and S8, a circuit is completed through coil 32, this circuit leading from switch 43, coil 32, lead 34, contacts S5, 86, lead 8l', Icontact 58, and arm 12 to ground. Upon energizing coil 32, the right rudder is moved toward open position. When the right rudder I5 moves to open position, it increases the drag on the right wing, thereby tending to cause the aircraft to turn to the right. When the right wing rudder l 5 is in operated position, the left wing rudder is in unoperated position. It is evident, therefore, that onlyY one rudder is operated at a time.

It may be seen that if it is now desired to close the right rudder, the energization of relay 43 of ampliiier 4G must be effected. Relay 43 closes switch 44. Switch 44 controls coils 35 and 33. The circuit through coil 35 is broken at contacts 64 and 65 due to the fact that follow-up member 93 is at the extreme right when the right rudder is fully operated. The circuit through coil 33 is closed through lead 86, contacts 8l and 55 to ground. The right 'wing servomotor 39 therefore operates in the reverse direction to close its rudder members l5 and to move its follow-up member toward the left. Servomotor 3Q may continue to operate its shaft 2i) until the member 36 reaches its extreme left position. At this time, the circuit for relay coil 33 is open at contacts 8l and E5. If coil 43 is deenergzed at this time, switch 44 will open and both rudders will be in unoperated position. Switches e4 and d5 may be of the spring loaded type which have their arms normally biased toward open position, such biasing means not being shown.

The control signal input for amplifier 49 across terminals iII and 42 is derived from a group of connected impedance networks ll, |60, and |80 by means of a circuit comprising terminal d2 of ampliiier dii, lead ISI, network Iill, lead II, a Contact |52, a switch arm |5i, lead |12, network lead V55, network I, ground |93, and back to the grounded side @I of amplifier dil.

rIhe impedance network ||l| is in the form of an impedance bridge. Two legs of this bridge are formed oy a resistor |62. One end of resistor |02 is connected through a lead |3 and a resistor lli to one end of a secondary |05 of a transformer |96. The primary of the transformer is indicated at Ir'. Since the secondary Iwindings of the transformers for other impedance networks may have a common primary winding, the reference character ||I`| is used in each case to indicate the primary winding. The other end of resistor I2 is connected through a lead It and resistor |9 to the other end of the secondary |05. Wiper |I| may engage the surface of resistor |62 and is adjusted therealong by a directional gyro ||3 through a mechanical connection |I2. The directional gyro H3 may be cf any conventional type. One suitable type is that disclosed in application Serial No. @147.989, filed June 22, 1942. The other two legs of the b-ridge are formed by resistors I2|l and |2I. lOne end oi resistor |2| is connected through a lead |22 to one end of secondary |85. The other end of resistor |26 is connected through a lead |23 to one end of resistor |2|. The other end of resistor |2| is connected through lead |24 to secondary |85. Wiper |25 engages the surface of resistor |23. Wiper |25 is connected through a lead |25 to one end of a resistor |2'i. The other end oi resister I2? is connected through a lead |28 t0 a wiper |29 which engages the surface of resistor |2|. Wiper |25 forms a portion or the followup means 3| operated by a servomotor 3|. Viper |29 forms a portion of the follow-up mechanism operated by servomotor 36. Resistor |27 has its center tap i3d connected through a lead 53| to input termina of amplifier 413'. The resistors It and which are connected between the ends oi resistor |92 and secondary |35 have adjustabie wipers |35 and liti-B which are connected together so as to move simultaneously in opposite directions. These Iwipers |3e and |36 with their respective connections i3? and |35 are used to shunt a portion of their respective resistors Iii and His. These resistors with their wipers are termed the centering means. The function of the centering means is to manually modify the position of either rudder. We may assume that in a given condition there is no potential difference between wiper ||I and contact |38 of resistor Suppose at a particular time the lei't end of secondary winding it is at a positive potential. IE under the conditions assumed the centering wipers |35 and |35 are lnoved clockwise it may be seen that the potential of Wiper I is increased due to the fact that the resistance between wiper I i I and the left end of the secondary winding |535 has been decreased. A dirference or" potential between wiper and the tap i3d will now exist. in order to raise the potential of tap it lwill be necessary to move wiper |25 to the left. Moving wiper |25 leitward increases the potential of tap I and such adjustment may be made until there is no dir"- ference of potential between Wiper and tap |33. The movement of wiper |25 is obtained from member 9|. Member 9| s driven from a left rudder servomotor. The left rudder servomotor also operates the left rudder consequently in obtaining the balance between the potentials of wiper and tap I3@ we have adjusted or changed the position of the left rudder. If it were desired that the position oi the right rudder were changed the centering means would have been moved in the opposite direction from that given for the adjustment of the left rudder. In Figure 4 the centering inea-ns had been adjusted to provide an arrangement so that the left rudder is normally carried in a partly open position.

A resistor Ill-Q is connected across the ends of secondary |65. A connection |f|2 leads from the center tap oi resistor its to one end of a resistor |43. The opposite end o1 resistor |43 is connected by means of lead IM to wiper III. A wiper i may be positioned along the surface of resistor Ii. A resistor |55 is also connected across the ends of secondary |5 of the transformer. A Wiper H6 may be positioned over the surface of resistor |55. This wiper |46 may be moved through a mechanical connection |41 by the rudder bar (not shown) of the aircraft.

)In impedance network lili, the center tap |30 oi resistor i2?, the center tap Mi of resistor |40, the wiper and the wiper ll are normally at the same potential. The resistor |27 is connected to wipers |25 and V29. Ii Wiper I|| be moved to the left to thereby raise its potential with respect to center tap |38, the wiper |25 may be moved to the left over resistor |25 to raise the potential of center tap I3@ so that there is no difference of potential between the center tap wil and wiper ill. li wiper had, on the other hand, been moved to the right to raise its potential, the wiper |253 could have been moved to the right over resistor EI to raise the potential of center tap |30 since wiper 29 is connected through lead i'llrto resistor |2l. The wipers v|25 and 29 are operatively connected to their respective servomotors Si and 3G through connections 93 and 92. Ii wiper iii be moved to the left to raise its potential with respect to `center tap |3|| of resistor |27, such difference of `potential is applied on the one hand to input 42 and on the other hand through impedance networks ISD, |S to ground ||3 and to the grounded side 4I of amplifier dil. With wiper in this position, the phase of the votage applied to terminals |4| and SL22 is such that relay |33 is energized, and as shown the lei-t servornotor 3| is effective to move the wiper |252, to the left to raise the potential of center tap |39 until it is the same as that of wiper iii. It should be n ted that the potential on wiper |25 is applied to one end of resistor `|27 and the potential of wiper |29 is applied to the other end of resistor |2l. rIfhe center tap I3!! is therefore at the average potential between the wipers |2|5 and |29. When wipers |25, |29 are at their innermost or central position, the potential oi wiper |25 is the same as wiper |29 and center tap |35 is at the same potential as center tap of resistor iis'l. Since center tap |38 is at the average potential between Wipers |25 .and |2, its potential may be raised or lowered by the movement of either wiper |25 or |2. For example, assume that wiper |25 is at its extreme right position and wiper |29 is in its eX- treme right position. Assume that in a given half cycle of the line voltage the left end of secondary |65 is positive with respect to its right end. If Wiper be moved to the left to raise 9 its potential with respect to -center tap |4|, the potential of center tap |30 may be raised either by moving wiper |29 to the left, through its servomotor 30, away from the negative and of secondary |05 or the potential of center tap |30 may be raised by moving wiper |25, through its servomotor 3|, to the left where it is near the positive end of secondary |05. Wiper |29 in this particular case may be moved until center tap |30 is at thesame potential as wiper In the particular arrangement it was necessary to move wiper |29 since its servomotor 30 through its coil 33 was operative ywhen switch 44 was closed Whereas the servomotor 3| for moving wiper |25 was inoperative since the circuit through its coil 35 was open at contacts 64, 65. It is therefore seen that any voltage arising out of difference of potential between wiper and center tap |30 is oiset by an equal and balancing voltage arising out of the movement of the servomotors 3| and 30. The servomotors 3| and 30 are thus operated an amount proportional to the movement of Wiper and do not normally move so as to operate either of the extreme limit switches.

A connection |5| extends from wiper |50 of network |0| to a contact |52 of a double pole double throw switch. A connection |55 leads from wiper |46 to a contact |54 of this double pole double throw switch. This switch has two additional contacts |55 and |56. Switch arm |51 which may engage contact |52 or |55 is connected through a lead |12 to a wiper The other switch arm |58 which may engage contact |54 or |56 is connected to ground. Thus it is apparent that network |0| may be alternatively, automatically or manually controlled.

The lead |12 connects to wiper |1| of a rudder resetting and compensation impedance network |60. This impedance network |50 is in the form of a double potentiometer arrangement. One potentiometer consists of a resistor 6| and a Wiper |66 which engages its surface. Movement of wiper |66 is derived from a vertical gyro |14 through a mechanical connection |13. The vertical gyro |14 may be of the type disclosed in the aforementioned application Serial No. 447,989, filed June 22, 1942. The ends of resistor |6| are connected by means oi leads |52 and |63 to the ends of a secondary |64 of a transformer |65.

The primary of the transformer |65, as usual, is

indicated at |01. The resistor |6| has a center tap |61 which is connected through lead |68 to one end of resistor |69. The other end of resistor |69 is connected through lead |10 to the wiper |66. Resistor |69 and wiper |1| form a second potentiometer. Wiper |65 may be moved with respect to the center tap |61 to select voltages either positive or negative during any given halicycle, depending on the direction of movement of Wiper |56 with respect to the center tap |51. The voltage selected by wiper |65 is fed across resistor |69, and wiper |1| may select any desired portion of this voltage since it may be positioned along resistor |63.

One end of resistor |69 is connected through lead to a wiper |15 of a manual turn impedance network |60. Network |36 comprises a resistor |8| whose ends are connected to the ends of the secondary |84 of a transformer |85 whose primary is indicated by reference numeral |01. A wiper |90 may be positioned along the surface of resistor |8|. The resistor |8| has a center tap |66. Two resistors are symmetrically connected across wiper |90 and center tap |86. In one case, a resistor |88 has one end connected through a lead |83 to wiper |95. Leads |54 and |81 connect the other end of the resistor |88 to the center tap |86. one end thereof connected through lead |S| to wiper |96. The other end of resistor |92 is connected through leads |94, |81, to the center tap |86 of resistor |S|. The wire |34 is connected to ground at |33. Wiper |90 may be positioned along resistor |8l in either direction from the center tap |86 to pick up positive or negative voltages with respect to the voltage oi the center tap |85. Such voltage picked up by wiper |30 is applied across resistors |83 and |02. Wiper |15 may be positioned over resistor |83 to select any portion of the voltage picked up by Wiper |30. The voltage so selected by wiper |16 of network |33 is applied in series with the voltage selected by wiper |1| with respect to its center tap I 6? of .impedance network |60. These two voltages which are in series are then fed through lead |12, switch arm |51, contact |52, to wiper of impedance network |01.

In impedance network im, wiper and center tap |4| of resistor |40 are normally at the same potential. Wiper may be moved over the surface of |02 in either direction to increase or decrease its potential with respect to center tap |4|. Such diierence or potential between wiper and center tap |4| is applied across the resistor |43. Normally, the potential of center tap |30 of resistor |21 is the same as the potential of center tap |4| of resistor |48. The center tap |30 is connected to the input side 42 of amplier 40. The potential between wiper and center tap |4| of resistor |40 is normally the same as the potential between wiper and center tap |35 of resistor |21 or the input 42 of amplier 40. Such dierence of potential is applied to the ends of resistor |43 and wiper |50 may select any desired portion of this dierence of potential. Such diilerence of potential as selected by wiper |50 is in series with the potential from impedance networks and |80. It is therefore seen that a voltage signal arising out of any impedance network is transmitted to the aniplier input 42. The grounded side 5| of the amplifier 4G is common with the ground |93 of the impedance networks |00, |63, and iti.

Wiper |90 of impedance network |55 may be adjusted over the surface of resistor |81 by a manual turn control means 250 which is mechanically connected by means 26| to wiper |30. Turn control means 265 may be rotated in either direction. A reference line 255 is used to position the turn control means in normal position. The

' mechanical connection 20| of turn control 200 also drives a cam 202. This cam has a circular portion and a depressed portion, as shown. The cam 202 may be adjusted to operate three contact bearing spring arms 283, 264, and 205 whose contacts are normally separated. When cam 202 is rotated, it cams the upper arm 263 to cause the contacts on tie arms 263, 201|, and 205 to become engaged.

When contact arms 203, 264, and 205 are so engaged, a circuit is completed from battery 600, lead 208, contacts of arms 263, 264, lead EEO, lock 2|| of the directional gyro I3, ground 2|2, and ground 2|3 of battery 660. This lock may be of the type disclosed in application Serial No. 44'?,- 989, iiled June 22, 1942. The lock 2| is arranged between the output member of a directional gyro and the means operated by this output member. Motion of the directional gyro is transmitted through a member to a control means by a fric- The other resistor |92 hasv i i tion clutch, not shown. When lock 2H is energiaed it holds the control side of the friction clutch, but the other side which is driven Toy the directional gyro is permitted to move.

The lower contact of spring arm 204 engages an upper contact on spring arm 295 when 202 is operated to complete a circuit from battery 622, lead 223, contacts of spring arms 2211, 235, lead 226, electromagnet 2131 to ground and return to ground 2 i3 of cattery When electromagnet 231 is energized, it moves switch arm 214 to open the circuit for the erecting means of vertical gyro 116i similarly to that disclosed in application Serial No. 447,989, filed June i942. The electromagnet 221 and switch arm 214 are termed the erection cut-out for the vertical gyro 114. The erection means for the vertical gyro 114 maintains its rotor axis perpendicular to the earth but it is necessary to cut out erection means while the aircraft is in a turn to prevent false erection due to centrifugal force.

The elevons are mounted upon shafts, not shown. The right elevon is operated by a servomotor 2li-1 through its output shaft 226. lThe left elevon is operated by a servomotor 263 through its output shaft 262. servomotors 2151 and 243 may be of the type disclosed in the above mentioned application Serial No. 447,989, filed June 22, 1942. The right elevon servomotor 261 is controlled by an amplifier 225. The left eleven servomotor 223 is controlled from an ampliner 241. Amplifiers 225, 221 are similar to amplifier lili. The direction of rotation of the output shafts 2493, 242 of the respective servomotors 241, 21%-3 depends upon and Varies with the phase relationJ ship of the control input voltage to the amplifiers 245 and 221 with respect to that of a line voltage. For example, the control input terminals of amplifier 221 are indicated at 25E) and 251. The amplifier 221 is supplied with voltage applied across terminals 253 and 254i from a source of voltage 122 which may be the inverter of aircraft electrical system. If the control input signal applied across terminals 252 and 251 is of the same phase as the voltage supplied across terminals 253 and 254i, the servomotor 223 will rotate its output shaft 242 in one direction. On the other hand, if the phase of the input signal across terminals 252 and 251 is opposite to that supplied across terminals 253 and 25d, the servomotor 25.13 will rotate its output shaft 252 in an opposite direction. The elevons which are normally streamlined with respect to the surface of the wing may therefore be moved by their servomotors 2551, 2&3 either to a position above the wing or below the wing.

Amplifiers 2de and 2411 are controlled by input control signals obtained from a group of connected impedance networks 212, 320, and 120. rIhe input circuit of amplifier 221 is as follows: from input signal terminal. 251 through lead 269, coil 351, impedance network 21B, switch arm 235, lead 29E, impedance network 32s, lead 196, wiper 195i, network 185, and ground E93, to grounded terminal 2513 of amplifier 241,

Amplifier 2:35 is controlled from an input signal derived from input terminal 251, lead 221, coil 350, wiper 215, impedance network 21B, lead 510. switch arm 225, lead 2955, network 32e, lead 19E, wiper 125, network 122, ground 193 and to grounded terminal 256 of amplifier 265.

Impedance network 212 comprises a resistor 211 having its ends connected through resistors 212, 2111 to the res' ective ends of secondary 21e of transformer 211 having a primary m1. The ends of secondary 216 are also connected through leads 21S, 212 to the respective ends of resistor 282. A wiper 213 may be positioned over the surface of resistor 282. This wiper is driven from servomotor 243 through a mechanical coupling 283. The surface of resistor 21S may be contacted by a movable wiper 282 whose motion is derived from a Vertical gyro 112 through a mechanical connection 225. A resistor 285 whose surface may be engaged by wiper 215 is reversibly connected across the ends of secondary 216 as shown. The wiper 215 is driven from the right servoinotor 241 by means of a mechanical connection A resistor 2531 is placed in parallel to resistor 211 across secondary 216. A wiper 292 f engage the surface cf resistor 291. The wiper be positioned from a manual com trol stick (not shown) through a mechanical connection 2536i. rI'his stick is of the conventional type, and movement in the conventional aileron control manner operates the wiper 292.

Resistor 212 which connects resistor 211 with one end of secondary 2id has a wiper 32o and lead 321 for shunting a portion of this resistor. Similarly, resistor 21d has a wiper 362 connected to a lead 393 whereby portions of resistor 214 may be shunted. Wipers Bilt and 322 are mechanically connected so as to operate together. The resistors and wiper constitute the centering means for network 21o.

A resistor 231e is also placed in parallel to resistor 211 across secondary 211i. Resistor 281a has a center tap 221! connected through a lead 22E to one end of a resistor 288. The other end of resistor 228 is connected through a lead 289 to wiper 224 which hears on the surface of resistor 211. A wiper 229 may be positioned along the surface of resistor 283 to select any portion of the voltage between wiper 284 and center tap 282. Wiper 29o is connected through a lead 51 to a terminal 511 of a double pole double throw switch. Reference characters 293, 2941, and 291 indicate the other contacts of the switch. Switch arms 295 and 228 have their respective pivot points connected to lead 225 and to ground, respectively. Lead 296 connects the switch arm 295 with a wiper 362 of a coordinated turn impedance network 328.

Impedance network 32o comprises three potentiometers. Resistor 516 of the rst potentiometer has its ends connected through leads 311, 312 to a common end of a secondary 353 of a transformer 31:1 having a primary 1111. The resistor 31o has a center tap 315 connected through a lead 316 to the other end of secondary 313. A wiper 218 may contact the surface of resistor 310. The motion of wiper 318 is derived from a directional gyro 113 by means of a mechanical connection 31S. Wiper 318 is connected through a lead 32| to one end of a resistor 322. The other end of resistor 322 is connected through a lead 323 to lead 316 and thence to one end of secondary 313. A lead 325 connects wiper 306 to one end of resistor 3135. The lead 32S connects the other end of resistor 325 to a center tap 321 of resistor 322. A wiper 338 may be positioned along the surface of resistor 325. The wiper 330 is connected through lead 191i to wiper 195 of impedance network 18. The wiper 39S is operated concomitantly with wiper 318 through the mechanical connection SES from directional gyro 113. It may he seen that the resistor 3120i impedance network 326 has both of its ends connected to the same side of secondary 313' and its center tap is connected to the other end of sec- 13. ondary 3|3. Wiper 3|8 may be moved in either direction with respect to center tap 3|5 of resistor 3|0. Therefore, for either direction of movement of wiper 3|8 its potential with respect to the center tap is of the same phase.

The potential between wiper 3 I 8 and center tap 3|5 is applied across the ends of resistor 322. A center tap 321 of resistor 322 is connected through lead 326 to one end of resistor 305. Wiper 306, which is concomitantly moved with wiper 3|8 is connected to the other end of resistor 305 through lead 325. The potential between wiper 306 and center tap 321 is thereby applied across the ends of resistor 305. The voltage selected by wiper 306 with respect to center tap 321 is not merely proportional to the movement of wiper 306 through its connection 3|9 from directional gyro ||3 but is also a function of the voltage applied across resistor 322. This voltage applied to resistor 322, in turn, varies with the movement of directional gyro ||3. The voltage between wiper 306 and center tap 321 is thus not a linear function of the movement f gyro ||3` but is a higher derivative of such movement. The wiper 330 may be adjusted over resistor 305 to select any desired portion of the voltage drop between wiper 306 and center tap 321.

The purpose in connecting one end of resistor 305 to the center tap 321 of resistor 322 and having its other end connected to wiper 306 may be claried from considering the operation of the network. The operation of the rudders will be omitted at this time. The network 323 is to provide a signal which is to effect operation of the elevons in opposite directions or as ailerons. Assume in a half cycle that the right end of secondary 3|3 is positive with regard to its left end. Assume also that the plane is oil course in such a direction as to cause the directional gyro ||3 to move the wipers 3|3, 306, to the right. In this case, the right end of resistor 322 is positive with respect to the center tap and wiper 366 will select a potential which is positive with respect to its center tap 321. This signal may be applied through lead 236 to 'eiect control of the elevons as ailerons to bank the aircraft in an effort to bring the aircraft back on the desired course. Assume, on the other hand, that the right end of secondary 3|3 is positive with respect to its left end, but assume that the craft changes its heading so as to cause the directional gyro to move wipers 3|8 and 306 to the left. Wiper 318 even though moved to the left again has a higher potential than center tap 3|5 and will apply a positive voltage to the right end of resistor 322 with respect to the other end of resistor 322. The voltage selected by wiper 306 since it is moved to the left of the center tap is negative with respect to the center tap 321. Therefore, an opposite signal is set up from that derived in the first case. This signal will result in the application of opposite aileron from the first case. This is logical since the deviation has been in a direction opposite from that in the first case, 4and it would be desirable to bank the plane in an opposite direction from that obtained in the iirst case.

Network |00 is associated. with the control of the elevons as :ailerons in a similar manner to that in which it is associated with the control of the rudder. That is, operation of the turn control 200 may displace wiper |90 in either direction to select a voltage with respect to center tap |36. Such difference of potential is applied across the ends of resistor 32 and a portion of this may be selected by wiper |95. Such voltage selected between and ground |93 is applied in series to the voltage set up on resistor 305 between wiper 330 and the end of resistor 305 connected to lead 325. In normal operation when the turn control 200 is operated, the lock 2|| prevents movement of wipers 3|8 and no signal is derived from network 326. The voltages thus added are applied through lead 295 to switch arm 295 and contact 292 to wiper 293 of impedance network 210. The voltage thus applied to wiper 290 with netwerk 210 in a balanced condition alters equally the potential of all points on network 210. Such potentials are therefore transmitted through network 21) through wiper 213, secondary winding 35|, and lead 233 to input terminal 25| of amplifier 241 on the one hand and through `wiper 215, secondary winding 350, lead 26|, and to input terminal 251 of amplier 245 on the other hand. The amplifiers will therefore become conducting. The ampliers 245 and 241 are so related to their respective servomotors 24| and 233 that even though the amplifiers 245 :and 241 as thus arranged receive the same input signal, the servomotor shafts 243 and 242 are rotated in opposite directions to secure the aileron action of the elevons.

The servomotors 24| and 243 when energized operate their follow-up members 231 and 283, respectively, to position wipers 215 and 213. It should be noted that resistor 236 is connected across secondary 216 in an opposite arrangement from that of resistor 282. This is necessary because its wiper 215 as driven by follow-up member 281 must set up an equal and opposing voltage to that which initiates the operation of its servomotor. Therefore. if wiper 213 moves to the left to set up an equal and opposing voltage to that which initiated the operation of its amplier 241, the wiper 215 must in eifect move in a direction to change its potential by the same amount as wipers 213 has its potential changed. Since the servomotor shafts operate in opposite directions, and wiper 215 would move to the right if wiper 213 moved to the left, the right end of resistor 286 must be connected to the same end of secondary 216 to which the left end of resistor 282 is connected.

The amplifiers 245 and 241 are also controlled to effect the operation of the elevons through their respective servomotors 24| `and 243 of such nature that the elevons move together in the same direction as conventional elevators. To effeet such control` ampliers 245 and 241 `are connected respectively to secondary coils 350 and 35| of a transformer 355 whose primary is indicated at 351. The primary 351 is energized from its control impedance networks 330 and 400. One side of the primary 351 is connected through a lead 358 to a wiper 36| of pitch axis deviations controlled impedance network 360. From here the control circuit for ampliers 245, 241 is completed through impedance network 353, a wiper 31|, contact 312, switch arm 31B, lead 330, impedance network y433, and lead 4|!) to the other end of primary 351. The impedance network 363 comprises a resistor 332 which has its respective ends connected through leads 363, 364, to the ends of a secondary 355 of a transformer 361 whose primary is indicated at |01. A wiper 368 engages the surface of resistor 362. This wiper 368 derives its movement from the vertical gyro |14 through an operative connection 369. The connection 330 partakes 0f the movement of the vertical gyro |14 resulting from movement of the plane about its pitch axis. Wiper 368 is connected through a lead 314 to one end of resistor 315. The opposite end of the resistor is connected through a lead 313 to a center tap 393 of a resistor 39|. The wiper 31| engages resistor 315 and is manually adjustable with respect thereto. The resistor 39| has its ends connected across the secondary 355 of transformer 351 through leads 383 and 35d. An additional resistor 3Std is connected across the ends of secondary 365 through leads 35m, 332. A wiper 333 may be positioned along the surface of resistor 393er. Wiper 353 is connected through an operative connection 393 to the conventional control stick (not shown.) of the aircraft. The fore and aft movement of this stick effects the movement of wiper 393. Lead 335 extends from wiper 393:1 to a contact 355 of a double pole double throw switch. The remaining contacts ci the switch are 391, 398, and 312. A switch arm 313 may engage either contact 312 or 331. A lead extends from the switch arm to one end of a resistor 435 of a compensating up elevator-impedance network 433. The other switch arm `311 is connected to ground and also to one end of primary 351. The wiper 35i may be manually adjusted to balance or unbalance network 333. It serves as a centering means for the elevons.

Impedance network 433 comprises a resistor 43| which has its ends connected through leads 433 and 332, to a common end of a secondary |138 of a transformer 339 having a primary |31. The resistor 431 has a center tap 4|3 connected through lead 4H to one end of the resistor 435. The other end of the resistor 535 is connected through lead M2 to wiper 4|3. Wiper 4|3 may be positioned over the surface of resistor 411i. Wiper 4|3 is actuated through an operative connection 4M by the vertical gyro |14. The actuation of wiper 4|3 is obtained from gyro |13 which responds to the movement of the plane about its roll axis. A lead 3|5 forms a junction with lead 4H to connect the center tap of resistor 53| to the other end of the secondary 338 from that to which the ends of the resistor 43| are connected. It may be seen that in any half cycle the wiper 4|3, although moved in either direction with respect to its center tap 4|3, always selects a voltage of the same polarity since the ends of resistor 23| are connected to a common source of potential. If wiper H3 be positioned with respect to its center tap i3 to select a voltage, this voltage is applied across resistor 335. Wiper i136 may be positioned along resistor 335 to select any portion of this voltage selected by wiper cl3. This voltage is applied from wiper 435 through lead 4| 8 to the primary 351. The circuit is completed through network 353, lead 313, resistor 315, Wiper 31|, contact 312 switch arm 316, leadv 333, to the other end of resistor 435. The primary 351 as thus energized thereby energizes secondaries 35| and 353 to cause their respective amplifiers 24'5 and 241 to operate. The networks 353 and 433 are to effect the control of elevons as elevators.

It may be recalled that servomotors 24| and 243 operate in reverse directions for the same signal applied to their amplifiers 245 and 241. Therefore, in order that the servomotors 24| 243 rotate their output shafts 243 and 242 in the same direction for elevator operation of the elevons, it is necessary to couple one secondary coil 35i to its primary 351 in a reverse manner from that in which the other secondary is-coupled. For this purpose the lower end of secondary 353 is connected to the input terminal 251 of amplier 245 whereas secondary 35| has its upper i6 terminal connected to the input terminal 25| of amplifier 241. By this circuit arrangement, the servomotors 24| and 243 will rotate their output shafts 243 and 242 to move the elevons in the same direction.

The same follow-up means 281 of servomotor 23| and follow-up 283 of servomotor 243 operate respective wipers 215 and 213 to set up in series with the respective secondary coils 353 and 35| balancing voltages equal and opposed to that supplied from primary 351. For example, assume in a half cycle that the upper end of secondary 35i is positive with respect to its lower end at the time that networks 213, 3i3, and |83 are in balanced condition. The resultant operation of the servomotor 243 will, through its follow-up means 233, effect the positioning of wiper 213 so that it is negative with respect to center tap 233 of resistor 281 which center tap is connected through network 323, 33 to the grounded terminal 253 of amplifier 241. Since wiper 213 being connected thereto is at the saine potential as the lower end of secondary 35|, the grounded terminal 253 is at a higher potential than the lower end of secondary 35|. The amount that the potential of terminal 253 is above the potential of the lower end of secondary 35| depends upon the movement given to wiper 213. Eventually, a point is reached where the terminal 253 and the terminal 25| of amplifier 241 have the same potential with respect to the lower end of secondary 35| at which time the amplifier 241 no longer operates.

It may be seen that the double pole double throw switches 533, 50|, and 532, when moved to an opposite position from that in which they are illustrated in Figure 4, serve to transfer control of the networks to the manually operated rudder bar and the flight control stick (not shown). In network 363, the operation of the control stick by the pilot will move, through its connection 335, wiper 333. The movement of wiper 333 enables it to select a voltage with respect to slider 36|. Wiper 333 is connected through lead 335, terminal 336, switch arm 311, to one end of primary 351. The other end of primary 351 is connected through lead 358 to wiper 33|. This signal resulting from the movement of wiper. 393 is applied to the primary 351 to cause it to energive the Secondaries 353 and 35|. The secondaries 353, 35| in turn operate their amplifiers 245 and 23'! tc eiect operation of the servomotors 22| 243. The servomotors actuate their output shafts 223 and 2&2 to eiect movement of the elevons in the same direction. Similarly, movement of the control stick or" the plan athwartships effects movement of wiper 232 by means of the connection 293:1. Wiper 292 when thus moved selects a potential with respect to center tap 233 of resistor 231. This potential is applied through lead 292e to contact 291, switch arm 238, to ground and to the amplier ground terminals 25E! and 255. The other input terminals 25|, 251 of the amplifiers 241, 245 are connected on the one hand through lead 263, and secondary winding 35| to wiper 213 and on the other hand through terminal 251, lead 26|, and secondary winding 353 to wiper 215. At this time, the wipers 213 and 215 being centered are at the same potential as the center tap 283 of resistor 281. A signal is thus applied to ampliers 245 and 231 to cause the operation of servomotors 24| and 243 to drive their output shafts 243 and 242 in opposite directions to position the elevons in opposite directions. The operation of the servomotors 24| and 243 positions the follow-up connections 283 and 281 to position the wipers 213 and .215 with respect to their center positions to Set up an equal and opposing voltage on their respective amplifiers to that set up by the movement of wiper 292. No control signal is applied to amplifiers M5, 241 and they cease controlling their servomotors 24|, 243.

When double pole double throw switch 502 is thrown to the right from the position shown in Figure 4, movement of the rudder bar, not shown, causes movement of Wiper |46 through the operative connection |41 to select a voltage with respect to center tap |4| of resistor |40. This signal voltage selected by movement of wiper |46 is transmitted through lead |59, contact |54, switch arm |58, switch arm terminal |53 to ground and to the grounded terminal 4| of amplier 40. At this time the rudders are considered as closed with wipers |25, |29 in the inner positions and the potential of center tap |30 of resistor |21 is the same as that of center tap |4| of resistor |40. Center tap |30 is connected to input terminal 42 of amplifier 40. The signal as thus applied to amplier 40 causes the ampliiier 40 to eiect operation of one or the other of servomotors 3| and 30. These servomotors, when operating, position their respective rudders and also actuate their follow-up means 93 on the one hand and 92 on the other hand to position their follow-up wipers |25 or |29 to balance the voltage resulting from the movement of wiper |46.

Operation The operation of the system will be recited with reference to Figure 4 and to the diagram shown in Figure 3. The operation of the system when control is elected by the manual turn control means 200 will be considered iirst. The operation of the turn control means eiiiects operation of the directional arm lock 2|| and also renders ineffective the erecting system for the vertical gyro |14. Turn control 200 also positions a wiper in network |80 to derive a signal for control of the rudder and a further signal for control of the elevons. The signal applied to the rudder control causes the operation of amplifier 40 which positions one or the other rudder, depending on the direction in which the turn is to be made. At the same time, a signal is applied to the elevon amplifiers 245 and 241 from the turn control impedance network |80, lead |96, network 320, lead 296, network 210, lead 260, to 'amplifier 241 on the one hand and through wiper 215, lead 36|, and input terminal 251 of amplilier 245 on the other hand. This causes the servomotors to position their elevons in opposite directions. The plane turns and banks under the dual action of the rudder and ailerons. The banking of the airplane causes the vertical gyro |14 to set up control signals due to movement of the plane about the roll axis. These signals are sent to networks 400, 360 which may be termed the elevator networks; the networks |80, 320, and 210 which may be termed the aileron networks; and to networks |86, |60, which maybe termed the rudder networks. The elevator networks cause the operation of the elevon ampliers 245 and 241 to move the elevons through their servomotor in the same directions. In other words, the elevons are given an up movement whenever the plane is in a turn. It is desirable to give up elevator in turns since the plane tends to lose altitude when in a turn and the application of elevator tends to correct for any tend- 18' ency to lose altitude. The control signal derived from the vertical flight gyro |14 and applied to the aileron networks causes the ampliers 245 and 241 to effect operation of their servomotors 24|, 243 so that the elevons are moved toward normal position. In other words, the effect of this control signal in the aileron networks is to wash out the signal which was originally applied to this network through the operation of the turn control means 200.

The purpose in washing 0u the signal is clarified by the following explanation. When it is desired to place an aircraft in a particular angle of bank, it is necessary after that angle of bank is reached to move the control surfaces which obtain this bankV toward their normal positions. Otherwise the plane will continue to bank.

Similarly, the control signal from the vertical gyro and applied to the rudder networks causes the amplifier to effect operation of the servomotor 30 or 3| to move the rudder back to unoperated position. The purpose of applying rudder when making a turn is that the application of rudder along with aileron enables a plane to go into the turn more rapidly than if aileron alone were used to turn the plane. After the plane has started into its turn, the rudder may be placed in neutral position along with the ailerons or elevons, and the plane will continue to turn at the desired banking angle.

When it is desired to straighten out, the turn control 200 is moved back toward normal position. This sets up an opposite signal in the rudder and aileron networks. The rudder is moved in an opposite direction, as are also the ailerons or elevons. The movement of the elevons as ailerons causes the plane to lose some of its bank. This changes the amount of movement which vertical gyro |14 applies to the wiper 4|3 in the elevator network, the wiper 284 of the aileron network, and the wiper |46 of the rudder network. The resulting movement of these wipers in their respective networks again causes the movement of their control surfaces toward nor- I mal position. Continued movement of turn control 200 until it-reaches normal position causes repeated application ofopposite rudder and aileron and their re-centering by control signals coming from the vertical gyro |14. The action is continuous so that when the plane reaches level position the control surfaces are in neutral position and the respective networks are in balanced condition. r

The operation may also be considered when the plane is in level night and is being stabilized by the directional gyro I3 and the vertical gyro |14. If the aircraft deviates from its desired direction of night, the directional gyro |'I3 sets up a control signal in the aileron networks and in the rudder networks. The rudder networks effect the operation of the servomotors to apply rudder. At the same time, the aileron networks apply a signal to their amplifiers to effect movement of the elevons as ailerons. The plane now moves toward its desired-direction under the positioning of the elevons and rudder. The movement of the elevons as ailerons causes the plane to bank and thereupon causes the vertical gyro |14 to set up control signals in the elevator networks, the aileron networks, and the rudder networks. Again, the elevator network tends to apply up elevon to maintain the altitude of the aircraft. The aileron networks as controlled by the gyro |14 tend to restore the elevons to neutral position and the rudder networks restore the rudder to unoperated arrange positionr The pIa/neiii'es towardl its desired direc.- tion and in sov doing thef value of the deviation signal fromv the directional gyro. I1| 3 decreases'. Since the signal! is decreasing, the signal applied to thel aileron and. rudder networks causes the positioning of the elevons and rudder in a direction opposite from that originally given to them. The magnitude of the bank of: the plane: thereupon decreases. Thevertical gyroresponds. tothe lessening banking angle and effects the returnA of the rudder to neutral position and the elevons to neutral position and tends.v to.` cause the elevator network to restore the elevons' toward neutral position. rlhe action is continuous, lessening of the deviation signal. being used to apply opposite rudder and aileron from that'which itv originally caused to-be set up. Similarly, the vertical gyro responds to the lessening angle resulting from the opposite--movementof the controls. and tends to decrease the amount of up elevator and to restorethe elevons through. theaileron network and the rudder through the rudder networkv to zero position. Finally, as the planeV reaches its desired heading, the rudders and elevons are in normal position and the networks are in a balanced condition.

The operation will be considered when the plane, due to an external disturbance, has a movement about its roll axisr The. vertical gyro |14 responding to the. movement of thel plane aboutVA the roll axis, sets up asignal. in the elevator network, the aileron networkV and the rudder network. The. purpose of applying signal in the aileron network isv to raise the wing which has been depressed. 'I'he purpose of' operating the rudder is to prevent the plane from turning in the direction of the depressed wing; In other words, the rudder is operated to maintain the direction in which the plane. is: flying. They operation of the elevator networks is to provide up elevon to prevent the planefrom losing altitude. As the plane tendsttoregain level flight,

. the magnitude of the signal fromV the vertical signalfrom the verticalV gyro |14' decreases. still y further, the rudders and elevons are moved still more toward the normal position. When the plane regains level flight, the rudders and elevons are inV normal position, and the networks are in balanced condition.

Movement of the plane about the pitch axis does not result in the aircraft having a tendency to turn as would a movement about the roll axis. The movement of theaircraft about the pitch axis causes the vertical gyro |14" toV respond and set up a signal in the elevator network only to eiect up or down elevon, as the case may be. As the plane in response tothe movement given to the elevons moves toward level flight position, the value of the signal from the vertical eyro` to the elevator networks decreases. This causes the movementV of the elevonsl toward' normal position. As the plane moves toward level night, it eventually reaches a condition in which the networks are balanced, and the elevons are in unoperated position. y It can now be seen that this invention provides aV novel flight control. system for a tailless airplane in which two single. control surfaces serve a dual function. In one they control the movement of the plane about the roll axis, andinfthe other theyV control the plane aboutthe pitch axis. In these functions turn about the roll axis results in opposite movement of these control` surfaces and turn about the pitch axis results from the same direction of movement of these control surfaces.

The novel flight control system also includes a new apparatus for controlling the movement. of the plane `about the turn axis by increasing or decreasing the resistance. of a wing. With this arrangement maximum eiciency ofiiight is obtained by permitting only one wing resistance changing device to be placed in operated position at one time.

I claim:

1. In an automatic flight control system for an aircraft having two elevon control surfaces operable. in the same or opposite directions, anindividual operating means for each said control surfaces, means responsive to the tilt of the aircraft aboutY an axis for oppositely controlling saidoperating means to move said elevons in opposite directions, and further means responsive to the tilt of the aircraft about said axis for similarly and additionally controlling said operating means to move said elevons in but one directionV irre.- spective of said direction of tilt.

2'. In an automatic flight controlsystem for an aircraft having two control surfaces, operating means. for said control surfaces, a rst normally balanced control network, a second normally balanced control network adapted for controlling said operating means, said first control network being isolated from the other network, means responsive to the movement of said aircraft about an axis and connected to said control networks to unbalance said networks, means for transferring the effect of unbalance o f said isolated network to the second network whereby unbalance of either network causes the operation of said operating means.

3. Flight control apparatus for an aircraft having two elevon control surfaces, operating means for said control surfaces, normally balanced control networks adapted to control said operating means, one network controlling the operation of said elevons in the same direction, the other network controlling the operation of said elevons in opposite directions, means. responsive to the movement of the aircraft about one axis and adapted to unbalance said networks, and followup means operated by said operating means and adapted to render said control networks ineffective with respect to said operating mean's.

4. In a control system, a nrst impedance network, a second impedance network, transformer means comprising a primary winding connected across said first network and a secondary winding connected across said second network thereby intercoupling said networks, means for unbalancing said first network whereby a voltage signal derived from vthe first network is applied through the transformer coupling to the second network, a motor means having an amplifier connected to said second network and controlled by said first network through said second network, and a follow up means operated by said motor means and associated with said second network to set up in said second network a signal opposing that applied to said second network.

5. Flight control apparatus for an aircraft having two control surfaces for controlling the movement of the aircraft about an axis, individual reversible operating means for actuatingy each control surface, control means associated with said operating means for selecting the direction in which the aircraft is to be turned, and follow up means for each operating means, each said follow up means in one position controlling operation of its associated operating means and in another position controlling the operation of both operating means whereby only one control surface may be actuated at a time.

6. Flight control apparatus for an aircraft having two control surfaces for controlling said aircraft about an axis comprising, individual reversible motor means for actuating said control surfaces, a control means including motor control elements associated with said motor means for controlling the direction of movement of both motor means, followv up means actuated by said motor means, the follow up means of each operating means in one extreme position operating a control element to discontinue further movement of its motor means beyond said position, and in another extreme position operating a control element to discontinue further movement of its motor means beyond said other position and to condition said other motor means for operation by said control means.

7. Flight control apparatus for an aircraft having two control surfaces for controlling the movements of the aircraft about an axis, individual reversible operating means for each said control surface, control means, an amplifier associated with said control means, means controlled by said amplifier for selecting the direction in which the aircraft is to be turned and controlling both operating means, and follow up means associated with each said operating means, the follow up means of each operating means in one position controlling its own operating means and in another position controlling the operation of the other operating means.

8. Control apparatus comprising two reversible motor means, control means connected thereto for selecting the direction of rotation of each motor means, and follow up means connected to said control means and operated by each motor means for terminating operation of each motor means, each follow up means in one position engaging rotation limiting means for controlling its motor means and in another position engaging rotation limiting and motor conditioning means for controlling the operation of the other motor means and stopping rotation of its motor vmeans whereby only one motor means is in operation at one time, said control means including a plurality of electrical signal generators and signal combining means for providing a balanceable network and operative connections from each motor means toone signal generator and means for operating a signal generator.

l 9. Fight control apparatus for an aircrafthaving elevons for controlling the movement of the aircraft about two axes, individual operating means for each elevon, a control means for each said operating means, means responsive to the movement of the aircraft about one axis and asso: ciated with said control means whereby said elevons move in opposite directions and means controlled by the movement of the aircraft about another axis and associated with said control means whereby said elevons are moved in the same direction, each control means including an amplifier having signal input terminals connected to a separate secondary winding the connections of one amplifier to its windings being the reverseof the connections of-l the other am- 22 pliiier to its secondary winding, and said responsive means includes a common primary winding for said secondary windings and an adjustable electrical signal generator connected across said primary winding and a tilt responsive means which on movement about one axis in either direction operates one signal generator to provide a voltage in proportion to said tilt but of constant phase and which on tilt about a second axis operates a second signal generator to `generate a voltage in proportion to said tilt but of a phase that varies with said tilt, said second signal generator being connected in like phase to each amplifler.

10. Control apparatus for an aircraft having two control surfaces which when moved in the same direction cause a change in the attitude of the craft about one axis and when moved in opposite directions cause a change in attitude of the craft about a second axis at an angle to the first axis, operating means for said control surfaces, means responsive to the attitude of the craft about said axes, a rst impedance network, a second impedance network, a transformer having a primary winding and two secondary windings oppositely disposed intercoupling said networks, means associating said networks with said operating means, means for unbalancing one network from said responsive means upon movement of the craft about one axis whereby said operating means moves said control surfaces in the same direction, and means for unbalancing the other network from said responsive means upon movement of the craft about said second axis to cause said other network to control the operating means to move the surfaces in opposite directions.

11. Control apparatus for a dirigible craft comprising: two attitude controlling power mechanisms operable in the same or opposite directions, rudder power mechanism, a control means for each mechanism, a rst electrical network for operating said attitude power mechanisms control means to effect movement of said mechanisms in the same direction, a second electrical network for operating said attitude power mechanisms control means to effect movements of said mechanisms in opposite directions, a third electrical network for operating said rudder power mechanism, means responsive to tilt about one axis for adjusting the second and third networks, and means responsive to tilt about an axis at an angle to said one axis to adjust said first network.

12. Control apparatus for an aircraft having elevons operable in opposite directions to control the craft about its roll axis and a pair of rudders operable to provide opposite control of said craft about a second axis, said apparatus comprising: elevon power means; rudder power means for each rudder; control means for said elevon power means, control means for said rudder power means providing individual period rudder operation, means responsive to tilt about one axis to effect operation of both control means to effect operation of said elevons and the operation of one or the other rudder.

13. Control apparatus for an aircraft having elevon control surfaces operable in the same or opposite directions to control the attitude of said craft about two axes, said apparatus comprising: elevon power means; control means for said power means; pick-off means aligned with said roll axis of said craft and responsive to tilt about said axis; and means in said control means operasse-,oec

23 ated by `said pick=ol responsive means for effect; ing'o'perat-ion of said elvons in the same or in opposite directions. Y

14. Control apparatus for an aircraft having two elevon control surfaces operable in the same or in opposite directions, said apparatus com-'- prising: elevon power means; normally balanced 'control networks adapted to control said power means; one network controlling the operation of the elevons in the same direction; the other network controlling the operation of the elevons -in the opposite directions; means responsive to tilt about one axis to unbalance Vone network; means responsive to tilt about a second axis to unbalance the second network; and follow up means operated by said 'power means and 'adapted to render' lsaid networks ineffective to control 'said power means lacking further movement of s'aid tilt responsive means.

15. In an automatic flight control system for an aircraft having elevons operable in the same 'or opposite directions for controlling the laircraft -about two axes and ru'dder's for controlling the aircraft about a third axis, operating means for said elevons, operating means for said rudders, means responsive to the movement of said aire craft about one axis, a first control network associated with said elevon operating means and -actuated by said responsive means upon tilt 'of the aircraft about said one axis to effect movement of the elevons in the opposite directions, an additional 'control network associated 'with "said elevon operating means and actuated by said responsive means upon tilt 'of the aircraft about said one axis to effect movement of the elevons in the same direction, and control means for said rudder operating means actuated by said responsive means upon tilt of the aircraft about said one axis.

16. Control apparatus for an aircraft having two control surfaces for controlling the attitude of the aircraft about an axis, said apparatus come `prising: a reversible motor means for each 'con` trol surface; a control means for operating each motor means, a balanceabl'e variable impedance network for operating said control means on unbalance thereof, a follow updriven by each motor means to rebalance said network, Vswitch means operated by each fol-low up means at one'extreme position thereof to render its motor means' two control surfaces for controlling the attitude 'of said aircraft about an axis thereof, said ap# paratus comprising: a power means vfor operating each control surface; amplifier means connected to each power means; a control circuit connected to said ampliner and containing a Dlurality of electrical signal generators, means for operating one signal generator to unbalance said circuit, means driven by each power means and operating another signal generator to rebalance 'said circuit, and means operated in one extreme position of a power driven means to prevent further operation of its power means beyond said position and to condition said other power means Afor operation by said amplifier means'.

18. Control apparatus for an aircraft having twoelevon surfaces operable in the same direction to change the attitude of the aircraft about lits lateral axis and movable in opposite direc# tions to 'change the attitude of the craft about its roll axis and rudder surfaces for 'changing the attitude of the craft about its vertical axis, said elevon and rudder control surfaces being located in the wing panels of said aircraft, said apparatus comprising: an individual motor for operatingY each control surface; tilt responsive means operable proportional to movement of said craft about the lateral axis for operating both elevon motors to move the elevons in the same direction, tilt responsive means operable proportional to movement of said craft about the roll axis for operating both elevon motors to move the elevons in opposite directions; means including follow-up means operated by each elevon motor to effect termination of its opera*- tion in accordance with the combined proportional effect of both tilt responsive means on said motor, and means for operating one of said rudder motors in proportion to the response of 'said roll responsive means.

19. n an automatic flight control apparatus for an aircraft having two rudder control sur-'- faces for controlling the attitude of Said craft about an axis thereof; a separate motor means for reversibly operating each control surface; control means for both 'operating means to effect their operation; means for providing signals of reversible phase to said control means to affect the operating means and thus the movement of said craft about said axis in either direction; and further means controlled by the positions of said motor means to determine which motor means will position its control surface in rea spense to a signal.

20. Control apparatus for an aircraft having two elevon surfaces operable in the same direction to change the attitude 'of the aircraft about its lateral axis and movable in opposite direc@y tions to change the attitude of the craft about its roll axis, said elevon control surfaces being located in the wing panels of said aircraft, said apparatus comprising individual motor for operating each control surface; tilt responsive means operable proportional to movement of said craft about the lateral axis for operating both elevon motors to move the elevons in the same direction; tilt responsive means operable proportional to movement of said craft about the roll axis for operating both elevon motors to move the elevons in Vopposite directions; and means including followup means operated by each elevon motor to effect termination of its operation in accordance with the combined pro portional effect of both tilt responsive means on said motor.

21. Flight control apparatus for 'an aircraft having two control surfaces; separate operating means for each said control surfaces; three normally balanced control networks arranged in two pairs, with one network common to both pairs with one pair adapted to control an operating means, said networks in each pair being connected through a magnetic coupling; folio i up means associated with one network in a pair and driven by its operating means; and means for unbalancirig the common network, whereby a voltage derived from rsaid common unbalanced network is applied through said coupliiigto the other network in each pair and each said other network is controlled by its follow-up to set an equal but opposing voltage signal to that applied by said common network.`

DAVID L. MARKSEN.

(References 'on vfollowi'lg page) 25 REFERENCES CITED Number The following references are of record in the 2367869 me of this patent: 214121547 2,415,430 UNITED STATES PATENTS 5 2,417,821 Number Name Date 2,464,629

1,565,097 Nummert Dec. 8, 1925 1,599,574 McShane et al. Sept. 14, 1926 1,811,149 Petersen June 23, 1981 Number 1,970,584 Stewart Aug. 21, 1934 10 431,350 2,173,538 McKellar Sept. 19, 1939 Name Date Jones Jan. 23, 1945 Northrop et a1. Dec. 17, 1946 Frische et al. Feb. 11, 1947 Hercum et a1 Mar. 25, 1947 Young Mar. 15, 1949 FOREGN PATENTS Country Date Great Britain July 10, 1935 Certificate of Correction Patent N0. 2,558,096 June 26, 1951 DAVID L. MARKUSEN It is hereby certed that error appears n the printed specification of the above numbered patent requiring correction as follows:

Column 2, line 48, for set read sets; column 9, line 4, for and read end column 10, line 62, after upper read spmng; column 12, line 56, for Wiper 218 read wiper Y318; o

and that thesald Letters Patent should be read as corrected above, so that the same may conform to the record of the ease in the Patent Oce.

Slgned and sealed this 2nd day of October, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant Gommz'ssz'oner of Patents.

Certificate of Correction Patent No. 2,558,096 June 26, 1951 DAVID L. MARKUSEN It s hereby certed that error appears in the printed specification of the above numbered patent requrmg correction as follows:

Column 2, line 48, for set read sets; column 9, line 4, for and read emi column 10, line 62, after upper read spring; column 12, line 56, for wiper 218 read wcper 31.8;w Y Y and that thewsewd Letters Patent should be read as corrected above, so that the same may conform to the record of the case in the Patent Oice.

S1gned and sealed this 2nd day of October, A. D. 1951.

[SEAL] THOMAS F. MURPHY,

Assistant Uommz'ssz'oner of Patents. 

